Free radical dye transfer photographic process

ABSTRACT

A DYE-TRANSFER PROCESS FOR PRODUCING MULTI-LAYER FULLCOLOR PRINTS BY SEPARATE EXPOSURE OF THREE SUPPORTED LIGHTSENSITIVE COMPOSITIONS TO IMAGING LIGHT FROM A COLOR NEGATIVE THROUGH GREEN, RED, AND BLUE FILTERS RESPECTIVELY, TO PRODUCE A MAGENTA, CYAN, AND YELLOW DYE IMAGE IN THE RESPECTIVE COMPOSITIONS. THE IMAGES ARE EACH TRANSFERRED, IN REGISTER, TO A TRANSFER SHEET IN THE PRESENCE OF A TRNASFER AGENT TO GIVE THE COLOR PRINT. THE LIGHT-SENSITIVE COMPOSITIONS, WHICH PRODUCE COLOR ON EXPOSURE WITHOUT DEVELOPMENT, COMPRISE A DYE BASE SUCH AS STYRYL, CYANINE OR MEROCYANINE IN COMBINATION WITH A ACTIVATOR COMPOUND SUCH AS CARBON TETRABROMIDE.

R. H. SPRAGUE 3,764,320

FREE-RADICAL DYE-TRANSFER PHOTOGRAPHIC PROCESS Oct. 9, 1973 Filed Nov. 15. 1970 mim. .Si IIL Q Q QQ A||||!.| Q QQ Q x Q All IIIV x BQmQ tm A I I il Q Rx@ SQ u Q Q @mmm n n x Q SEQ u Q hmmag. .3 .Q

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ATTORNEY United States Patent O1 nce 3,764,320 Patented Oct. 9, 1973 3,764,320 FREE-RADICAL DYE-TRANSFER PHOTOGRAPHIC PROCESS Robert H. Sprague, Chelmsford, Mass., assignor to Itek Corporation, Lexington, Mass. Continuation-impart of abandoned application Ser. No. 658,424, Aug. 4, 1967. This application Nov. 13, 1970, Ser. No. 89,534

Int. Cl. G03c 5/54 U.S. Cl. 96-29 D 13 Claims ABSTRACT OF THE DISCLOSURE A dye-transfer process for producing multi-layer fullcolor prints by separate exposure of three supported lightsensitive compositions to imaging light from a color negative through green, red, and blue filters respectively, to produce a magenta, cyan, and yellow dye image in the respective compositions. The images are each transferred, in register, to a transfer sheet in the presence of a transfer agent to give the color print. The light-sensitive compositions, which produce color on exposure without development, comprise a dye base such as styryl, cyanine or merocyanine in combination with an activator compound such as carbon tetrabromide.

CROSS-REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of Sprague, Ser. No. 658,424, filed Aug. 4, 1967, now abandoned.

BACKGROUND OF THE INVENTION (1) Field of the invention The present invention relates to a free radical dyetransfer photographic process.

(2) Description of the prior art U.S. Pats. 3,100,703, 3,102,810, and 3,109,736 disclose light-sensitive direct print-out photographic systems not employing silver and not requiring development. In general, the systems employ a light-sensitive composition comprising one or more styryl, cyanine, or merocyanine dye bases in combination with a light-sensitive free-radical generating organic halogen compound. Upon exposure of such a composition to imaging light, usually with the composition in the form of a film or coated sheet, a negative of the image is formed immediately in the lightsensitive sheet to produce a direct print-out negative copy.

Many other free-radical light-sensitive systems have also been disclosed in the prior art. Some of these will be referred to infra.

SUMMARY OF THE INVENTION According to the present invention, systems like those mentioned above have been modified to render them adaptable to a dye-transfer photographic process useful for producing monochromatic negative photocopies and, particularly, for producing positive color prints from color negatives. The transfer processes now known in the art, such as silver diffusion, Polacolorj the Eastman dye-transfer process, or Technicolor imbibition process, have the disadvantage of employing silver systems which require considerable wet processing. This processing is complex, time consuming, and costly. Silver diffusion generally requires -30 seconds. Prior art dye transfer techniques may require one to two minutes in the transfer step alone. In contrast, in the system of the present invention silver is not involved and there is no wet processing of the type now common in the art. The present invention has the advantage of simplicity, speed, and economy.

The transfer processes of the present invention require only a few seconds and are substantially complete on contact of a transfer sheet with an exposed light-sensitive material.

To prepare a color print according to the present invention, a suitable supported light-sensitive composition comprising a dye base such as disclosed in the aforementioned patents, in combination with an activator compound, is first exposed to imaging light from a color negative through a blue, green or red filter. A corresponding yellow, magenta, or cyan positive dye image is produced in the light-sensitive sheet by reaction of an appropriate dye 'base with activator generated in the cornposition by the exposure. The resulting positive image is then transferred to a transfer sheet in the presence of a transfer agent, suitably after removal of unreacted lightsensitive material from the exposed supported composition.

A second light-sensitive composition is then exposed to the same color negative through a second colored filter (eg. a green or red filter in case of a first exposure through a blue filter to give a yellow positive) to produce a corresponding magenta or cyan positive. Again, the positive print is transferred, this time in register with the image first transferred.

Finally, a third exposure is made through an appropriate filter (e.g. red if the first two exposures have been through blue and green filters) to produce a cyan positive image. This image also is transferred to the same transfer sheet in register with the two previously-transferred images to give a color positive of the color negative ernployed. Since dye images in the three color positive prints are produced on exposure, without development steps, and since the transfer of these dye images to a receptor sheet can be effected by contact in the presence of only a very small quantity of transfer agent at the interface, substantially no wet processing in the ordinary sense is involved in the present invention. The utility of the process for the production of color prints, for example for large color prints or of release prints on movie film, is evident. The process also affords rapid production of monochromatic proofs useful to color printers when printing from screen plates.

BRIEF DESCRIPTION O-F THE DRAWINGS The figures illustrate the exposure and transfer of a hght-sensitive system of this invention to produce polychromic prints.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a broad embodiment, the process of this invention is useful with free-radical photographic systems which produce print-out images upon exposure to actinic radiation. These photographic systems include at least a dye base and an activator compound which acts, upon eX- posure to convert, the dye base to a colored dye image.

The patent literature contains descriptions of many of these systems. Some representative examples include: furfurylidenes and primary aromatic amines and lower halohydrocarbons (U.S. Pats. 3,394,391 and 3,394,394; British patent specification 1,093,724); ferrocene derivatives and iodoform (British patent specification 1,056,- 768); acridine, cyanine, merocyanine or styryl compounds with photoactivators comprising halogenated organic sulfoxides or sulfono compounds (Netherlands patent application 6614847); bis(paminophenyl)vinyl carbonium polymethine dyes in their leuco form with halogen-containing substances (U.S. Pat. 3,275,442); linear polyketones with hydrogen halide precursors (U.S. Pat. 3,268,- 333); polymers of cyclopentadienes or cyclohexadienes with halogenated methyl activators (U.S. Pat. 3,201,240;

British patent specification 1,056,767); combinations of a halogenated hydrocarbon, an indole, a ferrocene, and an aldehyde (U.S. Pat. 3,423,206); azoaniline or azomethine dyes with halogen-containing compounds capable of producing free radicals (U.S. Pat. 3,503,744); organic azide compounds with coupler compounds (U.S. Pat. 3,282,693); leucocyanide dyes combined with organic heterocyclic compounds which generate bitunctonal coupling intermediates upon exposure (U.S. Pat. 3,285,- 743); acid addition salts of substituted leucocyanide triphenylmethanes with metal perchlorates (U.S. Pat. 3,418,128); sulphazides with aromatic dye-forming compounds (British patent specification 1,094,288); colorless, oxidizable nitrogen-containing, organic color lgenerators together with photo-oxidants and reducing aents (U.S. Pat. 3,390,995); leuco forms of dyes with diacylazino compounds (U.S. Pat. 3,364,030); leuco forms of dyes with N,N,O-triacylhydroxylamine (U.S. Pat. 3,359,109); leuco forms of dyes with aromatic bitriazoles (U.S. Pat. 3,360,370); N-acyl-amino-phenoxazines, phenothiazines or dihydrophenazines toether with non-volatile nitrogencontaining photo-oxidants (U.S. Pat. 3,395,018; aromatic amines with organic halogen-containing activators (U.S. Pats. 3,042,515 and 3,042,516); N-vinyl compounds with organic halogen-generating activators (U.S. Pats. 3,042,- 517, 3,042,518 and 3,042,519); styryl dye bases With organic halogen containing compounds (U.S. Pat. 3,095,303); cyanine dye bases and organic halogen-containing compounds (U.S. Pat. 3,100,703); merocyanine dye bases and organic halogen-containing compounds (U.S. Pat. 3,102,027); colorless leuco dihydroanthracenes with either organic halogen or sulfur compounds (U.S. Pat. 3,342,595 )g etc. The above list is intended to be representative of the broad number of print-out photographic systems formed from dye bases and activating compounds which can be used with the present invention. This listing is not intended to be all inclusive.

The preferred color-forming systems for use in this invention are those systems formed from styryl, cyanine, or merocyanine dye bases together with free radical generating organic halogen compounds.

Numerous styryl, cyanine, and merocyanine dye bases useful in the present invention are disclosed in some of the aforementioned U.S. patents, which are incorporated herein by reference, where their formulas and syntheses are described in detail. For example, suitable styryl dye bases are those of the formula Ntri-onni(e=orr on=ommr -N RII 1 Rl wherein R and R are lower alkyl or benzyl, and may be the same or different; R" is -H or -CN; d and n are each 1 or 2, m is a positive integer not greater than 4; the sum of n-l and m-l is not greater than 4; and Q represents the non-metallic atoms (i.e. C, O, S, Se, and N) necessary to complete a heterocyclic nucleus.

Suitable cyanine bases are those of the formula n-N'on=on)`d,o=(oH-CH)1=b-con-ou)li\r wherein d and e are each 1 or 2; n is an integer from 1 to 4; R is alkyl, aralkyl, or aryl; R' is H or -'CN; and Q and Z represent the non-metallic atoms necessary to complete a heterocyclic organic nucleus having 5 or 6 atoms in the ring.

Suitable merocyanine dyes are those of the formula wherein R is lower alkyl or benzyl, R2 is lower alkyl, aryl, or benzyl; R3 is -H or -CN, a is 1 or 2; b is an integer from 1 to 3; c is an integer from 1 to 3; d is 1 or 2; Y and Z each represent the necessary non-metallic carbon, sulfur, selenium, oxygen, or nitrogen atoms necessary to complete a heterocyclic organic nucleus containing 5 or 6 members in the ring; Q is oxygen, sulfur, selenium,

of the formula o-oH=oH-N(CHJ)2 \N/ is a dye base which on exposure to light in the presence of a free radical generating organic halogen compound of a type later described herein produces a vivid yellow dye. Synthesis of this dye is disclosed by Rupe et al., Helv. Chim. Acta 15, 1321 (1932) (cf. Chem. Abs. 27, 2446).

The unsyrnmetrical cyanine base 2-[3-(3-ethyl-2(3H) benzoxazolylidene)propenyljt quinoline, of the formula is a dye base which will produce magenta dye salts on exposure to light in the presence of a free radical cornpound. Preparation of this dye is shown in U.S. Patent 3,102,810.

synthesized in Example 4 of U.S. Pat. 3,109,736 also forms a magenta dye on exposure to light in the presence of an organic halogen compound.

The dye 4-[3-(3-ethyl-2(3H)benzothiazolyidene) propenyl] quinoline of the formula is a dye base forming a cyan dye on exposure to light in the presence of a free radical generating organic halogen compound. This dye is known from U.S. Pat. 2,345,094, for example.

These dye bases, or others forming yellow, cyan, or magenta dyes, when employed in light-sensitive compositions in a process of the type described earlier, can be used to prepare positive color prints from color negatives.

The free radical generating organic halogen compounds preferably used in the light-sensitive compositions of the present invention are also disclosed in the aforementioned patents and generally have the formula RCX3, where R is a monovalent radical which may be hydrogen, chlorine, bromine, iodine, alkyl, haloalkyl, aryl, aroyl, or aralkyl, and wherein each X is chlorine, bromine, or iodine and wherein not all of the Xs need be the same. A wide variety of compounds falling within this category is disclosed in the patents and includes CC14, CBr4, CHCl3, CHBr3, Cm3, CBfCla, C2Cl6, C2BI`6, C2HBI5, C6H5CBI`3, and

Of these materials, carbon tetrabromide has proved of particular utility since it can be easily incorporated into lightsensitive films or coatings and gives sensitive systems in combination with the styryl, cyanine, and merocyanine dye bases.

Although the organic halogen compounds just disclosed can be employed alone or in combination with the various dye bases to produce light-sensitive compositions useful according to the present invention, it has proved desirable also to include certain colorless non-toxic organic sulfur compounds such as those taught in U.S. Pat. 3,285,744 in the compositions. These additives function as accelerators, stabilizers, and color intensifiers.

These sulfur compounds include: disulfdes and hydrosulfides of the formula RSSR and RSH wherein R is the heterocyclic nucleus of a type common in cyanine chemistry; disulfides of the formula R' S S R' Ratti-S4 Lft-Rf where R2 is H, lower alkyl, or aryl; suldes having sulfide sulfur attached to a carbon atom in a heterocyclic ring in which the same carbon atom is attached to two atoms other than carbon; thioureas; and acyclic thioacetanilides. These activators include heterocyclic mercaptans such as 2-quinoline, 4quinoline, 2-pyridine, 4-pyridine, imidazole, benzimidazole, thiazole, benzothiazole, -naphthothiazole, oxazole, benzoxazole, -naphthoxazole, selenazole, benzoselenazole, thiazoline, rhodanine, tetrazole, etc. A preferred material is 2-mercaptobenzothiazole.

The preferred light-sensitive compositions of the present invention may be imbibed directly into absorbent substrate lms or may be coated onto an appropriate substrate, usually in the presence of a suitable binder. Thus, these compositions of the present invention, dissolved in a non-polar solvent such as benzene, have been imbibed directly into Mylar films having an absorptive coating of cellulose acetate-butyrate thereon. Alternatively, the light-sensitive materials can be formulated into a coating composition with a solvent and a plastic binder material such as polystyrene or polyvinyl chloride and then used to coat a substrate material such as paper, wood foil or plastic.

In the coatings prepared in this fashion, the styryl, cyanine, and/or merocyanine dye base, the organic halogen compound, and an accelerator (if present) are usually employed in amounts such that the dye base is present in an amount from 0.001 to 1.0 part by weight, the free radical generating organic halogen compound is present in an amout of 0.1 to 10.0 parts by weight, and the accelerator is present in an amount of from 0.001 to 1.0 part by weight per part by weight of film-forming plastic within the resultant sensitized coating. Variation of the proportions within the ranges indicated would depend on the sensitivity sought in the coating, the intensity of the color desired in the print, the intensity of the light source used for exposure, and the particular combination of dye base and free radical generating agent employed in a particular case, all of which is evident to and within the knowledge of one skilled in the photographic art.

In general, the dye bases and free radical generating materials contemplated in the present invention are soluble in non-polar solvents such as benzene, toluene, xylene, and other liquid aromatic hydrocarbons, in aliphatic hydrocarbons such as n-hexane, n-heptane, and petroleum spirits, in cycloaliphatic hydrocarbons such as cyclopentane and cyclohexane, and in heterocyclic materials such as dioxane and the like. Accordingly, these materials can be used to fix the monochrome print produced on exposure to imaging light from a color negative prior to transfer of the dye image from the print to a transfer sheet. By Washing the print with a predominantly non-polar solvent of the type described, unreacted dye base and halogen compound lare removed from non-light struck areas.

In contrast, the dyes produced by reaction of the dye base and free radicals on exposure of the light-sensitive compositions of the present invention to light are salts or salt-like materials. These materials are relatively insoluble in non-polar solvents, but are quite soluble in polar materials such as alcohols and ketones. Accordingly, the last-mentioned solvents, particularly the lower aliphatic alcohols, are particularly useful as transfer agents in transferring the dye image from a monochrome print to a transfer sheet.

The transfer sheet need not be saturated with the transfer agent in order to effect transfer of the dye. Indeed, the mere moistening of the interface between the transfer sheet and the dye image, generally accomplished by moistening the surface of the transfer sheet, is usually sufficient to transfer the salt-like dye to the transfer sheet.

The production of multi-layer full-color prints according to the present invention is illustrated in the accompanying drawing which schematically shows the reproduction of a color negative of an original scene comprising red, blue and green elements.

As shown in the drawing, a rst exposure to the negative is made through a green filter employing a sensitized sheet forming a magenta dye image on exposure. The monochromatic dye image is then transferred to a transfer sheet in a first transfer step.

A second exposure is then made through a blue filter to produce a yellow dye image which is transferred in register to the transfer sheet bearing the magenta image.

A third exposure of a light-sensitive layer forming a cyan dye is then made through a red filter. The cyan image is transferred in register to give a positive print reproducing the original scene.

A better understanding of the present invention and of its many advantages will be had by referring to the following specific example, given by way of illustration.

EXAMPLE Twenty-five parts of 2-[3-(3-ethyl-2(3H)-benzoxazolyl- 1dene)propenyl]quinoline and 50 parts by weight of 2- mercaptobenzothiazole were dissolved in about 3200 parts by weight of acetone. (Alternatively, an equivalent quant1ty of the dye base 3-ethyl-5-(3-ethyl-2(3H)-benzothiazolylidene)-2-(4-quinolylmethylene) 4 thiazolidone can be used as the dye base.) An equal volume of a 10% solution of polystyrene in benzene was combined with this solution. Fourteen hundred parts of carbon tetrabromide were then dissolved in the mixture which, after filtering to remove undissolved solids, was coated on a Mylar substrate.

After drying, the light-sensitive film was exposed to a photoflood lamp through a color negative green filter for 30 seconds. The sheet was rinsed briey in a hydrocarbon mixture to remove unreacted dye base and the magenta image which had been formed was then transferred to paper moistened with methanol by contact for about live seconds.

Another light-sensitive composition was prepared using the same materials in the same proportions, except that a corresponding amount of Z-p-dimethylaminostyryl benzimidazole was employed as the dye base in place of the quinoline dye taught above. A second sheet of Mylar sensitized with this composition was then exposed to the same color negative through a blue filter, with the direct production of a. yellow print in the exposed sheet. After washing with a hydrocarbon to remove unexposed and unreacted dye base and halogen compound, the yellow dye image was transferred to the same methanol-moistened transfer sheet earlier employed, in register with the magenta image already in the sheet.

Similarly, a cyan dye image was prepared and transferred in register by the formulation and exposure through a red filter of a supported light-sensitive coating containing 4-[3-(3-ethyl 2(3H)benzothiazolylidene)propeny1] quinoline to form the nal color print.

The plastics and solvents employed in preparing the coatings described in the example are not critical to the operation of the invention, and other equivalent materials can be used if convenient. For example, good light-sensitive coatings have been prepared on paper substrates using polyvinyl chloride as a film-forming binder dissolved in a solution of tetrahydrofuran.

It will be understood that the photographic system of this invention can also be used in a multi-layer system wherein only one exposure followed by one dye transfer step is necessary to produce a full-color print.

What is claimed is:

1. In the method for producing a photocopy by exposing a supported free-radical light-sensitive composition comprising an activator compound and a dye base, the improvement for producing a polychromatic color print which comprises exposing three of said compositions, each respectively containing a dye base producing a cyan, magenta, and yellow dye image upon exposure to imaging light from a color negative, whereby said cyan, magenta, and yellow dye images are respectively formed, and transferring by diffusion said dye images to a transfer sheet in the presence of a transfer agent comprising a polar solvent for the dyes.

2. An improvement of claim 1 wherein said activator compound comprises a free radical generating organic halogen-containing compound.

3. An improvement of claim 2 wherein said dye base is selected from the group consisting of styryl, cyanine, and merocyanine dye bases.

4. An improvement of claim 3 wherein said light-sensitive compositions are in the form of a coating on a supporting substrate.

5. An improvement of claim 4 wherein at least one of said light-sensitive compositions additionally contains 2-mercaptobenzothiazole.

6. An improvement of claim 4 wherein said polar solvent is an alcohol or ketone.

7. An improvement of claim 6 wherein unexposed, unreacted, light-sensitive composition is removed prior to transfer of the dye image by fixing in a non-polar hydrocarbon solvent.

8. An improvement of claim 6 wherein said dye base producing a yellow dye image on exposure in the presence of a free radical generating halogen compound comprises Z-p-dimethylaminostyryl benzimidazole.

9. An improvement of claim 6 wherein dye base producing a magenta dye image on exposure in the presence of a free radical generating halogen compound comprises 2 [3 (3 ethyl-2(3H)benzoxazolylidene)propenyl] quinoline.

10. An improvement of claim 6 wherein dye base producing a magenta image on exposure in the presence of a free radical generating halogen compound comprises 3- ethyl 5 (3 ethyl-2(3H)-benzothiazolylidene)-2-(4- quinolylmethylene -4-thiazolidone.

11. An improvement of claim 6 wherein dye base producing a cyan dye image on exposure in the presence of a free radical generating halogen compound comprises 4-[3- (3-ethyl-2(3H)benzothiazolylidene)propenyl] quinoline.

12. An improvement of claim 4 wherein the cyan, magenta, and yellow dye-producing compositions form three layers of a unitary multi-layer system which are simultaneously exposed to produce the desired color change.

13. An improvement of claim 4 wherein the cyan, magenta, and yellow dye image-producing compositions are separately exposed through a red, a green, and a blue filter respectively, and wherein the step of transferring said dye images is carried out in register to said transfer sheet.

References Cited UNITED STATES PATENTS 2,559,643 7/1951 Land 96-29 D 3,246,984 10/ 1962 Nagy 96-3 3,255,002 6/1966 Rogers 96--3 3,106,466 10/1963 Sprague et al. 96-90 3,100,703 8/1963 Sprague et al. 96-90 3,102.81() 9/1963 Sprague et al. 96-90 2,668,113 2/ 1954 Schwalenstoeker 96-52 OTHER REFERENCES O.G., Feb. 2.1, 1950, vol. 631, p. 882.

NORMAN G. TORCHIN, Primary Examiner J. L. GOODROW, Assistant Examiner U.S. Cl. X.R. 96-3; 101-463 

